I think Torque is alright. It is optimised very well and works excellently on older hardware, something that can't be said for most big bucks proprietary engines (e.g. the UDK). It is also very cross-platform. And not like
DirectX is that great anyway (like not being backwards and sometimes not forwards-compatible). I'm pretty sure Valve never made their engine open source by the way, but I may be wrong on that. Torque can scale very well with minimal skill.
Also, consider how difficult it is for indie and open source developers to make an engine like CryEngine. Then add the hundreds of almost cinematic-quality assets that go into a game like Crysis. Impossible, that is.
By the way, the Quake engine (and similar, Call of Duty for one is based off of it) and CryEngine for example have different goals. Maps in arena shooters tend to be smaller not only due to the gameplay style, but also because they are much more detailed. In games with large maps the maps are usually not very detailed - just a long terrain with various techniques used to randomise the textures. Maybe a few trees and a building here and there.
Plus, you're kind of missing the point of games such as Quake. Quake and RE are
intentionally unrealistic. ARMA is no better a game because it's realistic. In fact, I find it horribly boring, the driving especially. 'It's your mission to save this island, now drive 700 km in that direction'. How about I get in my car and do that instead? But yes, different goals,
can't be compared.
Anyway, how powerful a computer that you have are we talking about here? You said about 5 years old. The video seems... very choppy. Recording software, of course, adds a very significant overhead.
Still, the work you've done is admirable (from what I understand you textured and morphed the whole map
by hand), but I'd pause there for a moment if I were you. You
have to think about the gameplay a bit. Consider the fact that a lot of research into real weaponry goes into ARMA, for instance. And vehicles. And sounds are, in fact (in ARMA's case), usually taken from the real-life version of the very gun you are holding in the game. Can you replicate that? Probably not, and hiring out a recording studio is very expensive.
You must take a step back and realistically think about what you want to do with your game. First, what you'd like the 1.0 version of the game to be ideally like, and second, if you can achieve all the goals you set out for yourself. Rewriting some of the core scripts in C++ (I think Torque supports accessing the API via C++) to make it scale better? Absolutely. Professional quality sounds from real guns and vehicles? Probably not. After you've done all that thinking
I just wanna say by the way, I don't want to dissuade you, I always like people who really believe in something. But I'm just saying,
be realistic about what you can do so you may one day actually finish the game.
Derek Yu's article on finishing a game is a classic, and I think any game developer should read it.
You just wasted 3 seconds of your life reading this.